System and method of monitoring a load condition of a vehicle

ABSTRACT

A system for indicating the state of load of a vehicle having suspension components comprising: 
at least one transducer (11) mountable on a single suspension component (3) such that a signal relating to the angular deflection of the suspension component can be generated; and 
a controller configured to receive the signal and generate an output representative of the state of load of the vehicle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/717,332 filed on Mar. 13, 2007. This application further claims thebenefit of Great Britain Application No. 0623806.6 0623802.6 filed Nov.29, 2006. The disclosure of the above application is incorporated hereinby reference.

FIELD

The present invention relates to a system and method for indicating thestate of loading of (for example) a commercial vehicle.

BACKGROUND

There are many reasons for fitting to a commercial vehicle a weighingsystem for indicating the state of payload or loading (e.g. payloadsafety and load optimisation). Commercial motor vehicles are designed tomove quantities of materials or goods on public roads. The vehicles aresubject therefore to the interests of local, regional or nationalauthorities who are particularly interested in vehicle overloading whichmay lead to possibly dangerous driving conditions for the operator andother road users. Another interest arises from the perspective of roador bridge damage by prolonged use by overloaded vehicles. Theresponsible vehicle operator also has a need to ensure that the payloadper journey is maximised safely for commercial reasons.

A commercial vehicle is typically made up of three major components fordescription purposes, namely multi-component suspension assemblies, achassis and a body. Each suspension assembly itself is made up of anumber of suspension components such as axle housings, beams, springs,damping components and bearings. Under loading conditions, thesesuspension components will move relative to each other and also relativeto the chassis or body.

Early weighing systems to indicate axle or vehicle overloading rely onsensors which react to the movement of one of these components relativeto another of these components within the suspension assembly or one ofthese components relative to the chassis or body. These early weighingsystems therefore rely on a dynamic device which is attached physicallyto a number of components that move relative to each other in order toindicate the relative position of one component to another. The dynamicdevice may be considered as a two (or more) part device and the extentto which parts move (or are affected by the movement of other parts) canbe related to the payload weight. One such device is disclosed in U.S.Pat. No. 6,566,864. A conventional weighing system of this type isadversely affected by the very harsh environmental conditions in whichit is installed and special measures are required to enable adequatesealing or shielding of the device in service. The weighing system isinherently susceptible to damage from large resilient objects caught orthrown up from a road surface. A device can be damaged if the axle orwheel encounters an over-travel event not typically seen in service(such as travelling on a particularly poor surface or as a result of avehicle collision).

SUMMARY

The present invention relates to a system for indicating the state ofloading of a vehicle which exploits a transducer intimately mounted onor attached to a suspension component of a suspension assembly.

Thus viewed from one aspect the present invention provides a system forindicating the state of loading of a vehicle having suspensioncomponents comprising:

a transducer mountable on a single suspension component such that asignal relating to the angular deflection of the suspension componentcan be generated; and

a controller configured to receive the signal and generate an outputrepresentative of the state of loading of the vehicle.

The system of the invention has the advantage that the transducer ismountable on a single suspension component and does not suffer thedisadvantages occasioned by debris and is resilient to over-travelevents. There are also no disadvantages as are typically experiencedwith systems of the prior art whereby mechanical wear can be asignificant drawback and the connecting portions of two or more piecesrequire sealing.

Typically the transducer is a one-piece measuring device. In a preferredembodiment, the system comprises a plurality of one-piece devices, eachmountable mountable on a single suspension component (eg close to avehicle axle). Preferably each of the plurality of one-piece devices ismountable on a different suspension component. Preferably each of theplurality of one-piece devices is mountable on a suspension component ofa different suspension assembly. Preferably a one-piece device ismountable on a suspension component of each suspension assembly (eg eachof the offside and nearside, front and rear suspension assemblies).

The transducer may be a static device. The transducer may be orincorporate an inclinometer or accelerometer. The transducer may bemountable close to a vehicle axle. The suspension component may be acomponent of a rubber suspension assembly, a trailing arm-typesuspension assembly, a leaf-spring suspension assembly or a damper (suchas a shock absorber or spring eg coiled or airbag spring) suspensionassembly.

The system may include a reference device capable of measuring the angleof inclination of the vehicle chassis or body. A knowledge of the angleof inclination of the vehicle chassis or body may be used to adjust thevalue of the angles measured by the transducers to allow use of thesystem on ground that is not level (ie on an incline).

The system preferably further comprises at least one reference deviceadapted to generate a reference signal relating to the attitude of thevehicle, wherein the controller is further configured to receive thereference signal and adapt the output signal representative of the stateof load to account for the variance in the or each deflection anglecreated by the attitude of the vehicle.

The (or each) reference device is typically fitted to the vehicle remotefrom the suspension assembly. The (or each) reference device may befitted to the vehicle chassis or body. Typically the (or each) referencedevice is fitted to an upper part of the vehicle chassis or body.

Preferably the controller output signal activates a sensory outputdevice.

The system preferably further comprises a display. Preferably thedisplay is the sensory output device. Preferably the display and thecontroller are integrated to form a single unit. Preferably the displayis used to program the controller.

The system may be configured to detect a disturbance. In a preferredembodiment, the controller is configured to detect whether the vehicleis subject to a disturbance. Preferably the disturbance is vehiclemovement, vehicle loading or vehicle unloading. Preferably thedisturbance detector is adapted to interrupt the sensory output of thesupervisory device during the disturbance.

Preferably each of a plurality of transducers is mountable on adifferent suspension component. Preferably each of the plurality oftransducers is mountable on a single suspension component of a differentsuspension assembly. Preferably a transducer is mountable on a singlesuspension component of each suspension assembly (e.g. each of theoffside and nearside, front and rear suspension assemblies).

Viewed from a further aspect the present invention provides a wheeledvehicle having suspension components comprising:

a system as defined hereinbefore, wherein the transducer is mounted on asuspension component.

Preferably the transducer is mounted close to a vehicle axle.

Preferably the wheeled vehicle comprises a suspension assembly at eachof the offside front corner, offside rear corner, nearside front cornerand nearside rear corner.

The transducer device may be mounted on (for example) a strut, leafspring or trailing arm of the suspension assembly. Typically thetransducer is intimately mounted (eg adhered or fastened) on an upperface of the suspension component.

In a preferred embodiment the vehicle has at least two front suspensionassemblies, each suspension assembly having at least one suspensioncomponent. Preferably the vehicle has at least two rear suspensionassemblies, each suspension assembly comprising at least one suspensioncomponent.

Viewed from a yet further aspect the present invention provides a methodof monitoring the load condition of a vehicle having suspensioncomponents comprising:

monitoring the deflection angle of the (or each) suspension component;and

generating an output signal from a controller which is representative ofthe load condition.

Preferably the method further comprises:

measuring the tare angle of at least one suspension component using aninclinometer or accelerometer mounted on a single suspension component,storing said angle in the controller and setting a lower thresholdcorresponding to said tare angle;

measuring the load angle of at least one suspension component using aninclinometer or accelerometer mounted on a single suspension component,storing said angle in the controller and setting an upper thresholdcorresponding to said load angle;

comparing the deflection angle to the upper and lower threshold andusing said comparison to determine the load condition; and

generating an output signal from the controller when either of the upperor lower threshold is reached.

Preferably the method further comprises:

measuring the attitude of the vehicle using a reference device mountedon the vehicle;

the controller receiving the reference signal and adjusting the tareangle and the load angle for the or each suspension component to accountfor the attitude of the vehicle prior to loading the vehicle.

In a preferred embodiment, the vehicle has at least two front suspensionassemblies, each suspension assembly having at least one suspensioncomponent, the method further comprising:

generating an output signal from the controller which is representativeof the

load condition with reference to the front suspension assemblies only.

In a preferred embodiment, the vehicle has at least two rear suspensionassemblies, each suspension assembly comprising at least one suspensioncomponent, the method further comprising the steps of:

generating an output signal from the controller which is representativeof the load condition with reference to the rear suspension assembliesonly.

Preferably the method further comprises:

setting an intermediate threshold, the value of the intermediatethreshold being between 30% and 98% of the value of the upper threshold;and,

the controller generating an output signal when the deflection anglereaches the intermediate threshold point.

Particularly preferably the value of the intermediate threshold isbetween 40% and 98% of the value of the upper threshold, more preferablybetween 50% and 98% of the value of the upper threshold, yet morepreferably between 60% and 98% of the value of the upper threshold(typically 80% of the value of the upper threshold).

Preferably the method further comprises:

monitoring the deflection angle of at least one suspension component attwo separate time intervals;

determining the difference of the deflection angles from the twoseparate time intervals; and

the controller generating a disturbance signal indicating that motion isdetected if the difference is greater than a pre-determined amount.

Preferably the method further comprises

the controller sampling the deflection angle at discrete intervals andstoring the sampled data as n sample sets each comprising a number ofsamples, where n is an integer; and

the controller generating a disturbance signal indicating that motion isdetected if the difference between two successive sample sets is greaterthan a pre-determined value.

In accordance with the invention, the state of loading or load conditionof the vehicle may be the payload or the applied payload weight, grossvehicle weight or axle weight. In accordance with the invention, thestate of loading of the vehicle may be a fraction of maximum fullloading or overload.

DRAWINGS

The invention will now be described in a non-limitative manner solely byway of example and with reference to the accompanying drawings in which:

FIG. 1 A view of a conventional coiled spring damper combination vehiclesuspension assembly.

FIG. 2 A view of a conventional suspension-monitoring device relying ontwo point mounting.

FIG. 3 A view of the conventional suspension-monitoring device of FIG. 2under an increased vehicle load.

FIG. 4 A view of a first embodiment of the present invention assembledon a spring damper suspension assembly.

FIG. 5 A view of a second embodiment of the present invention assembledon an airbag spring with remote damper suspension assembly.

FIG. 6 A view of a third embodiment of the present invention assembledon a leaf spring suspension assembly.

FIG. 7 A view of a fourth embodiment of the present invention assembledon a rubber suspension assembly.

FIG. 8 A schematic layout of an embodiment of the present invention.

FIG. 9 A flowchart illustrating operation of an embodiment of theinvention.

FIGS. 10 and 10.1 A flowchart illustrating the installation, calibrationand operation of an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In FIG. 1, an arrangement of components common to many vehicles isillustrated. The ground (1) is shown in section supporting a wheel (2)at a corner of a vehicle. Drive components are omitted for clarity. Thewheel (2) is attached to the vehicle by a hub (7) which is supported bya sprung damper assembly (6) and struts (3) (only one of which is shownfor clarity). The sprung damper assembly (6) and struts (3) which arecomponents of the suspension assembly have bearings at each end allowingconstrained movement of the hub (7). These bearings are attached topoints on a vehicle chassis (4) or body (5) depending on vehicle design.

In FIG. 2, a conventional weighing system is shown fitted to thesuspension assembly illustrated in FIG. 1. The weighing system consistsof two parts (9) and (10) intimately coupled together. The part (9) isconnected to the vehicle chassis (4) by a suitable fitting part (8). Thepart (10) is fitted to the strut (3). The parts (9) and (10) are fittedto their respective supports by bearings. The relative interaction ofthe two parts (9) and (10) is characteristic of the movement of thevehicle chassis (4) relative to the suspension assembly.

FIG. 3 shows the same suspension assembly illustrated in FIG. 2 butunder increased vehicle loading. The position of the strut (3) relativeto the vehicle chassis (4) or body (5) has changed and the sprung damperassembly (6) has reduced in length. It is clear that parts (9) and (10)are dynamic and move relative to each other either within themselves (orotherwise) or impart forces on each other. The relative movement orthese forces can cause problems with ingress of unwanted material intothe moving parts or over-travel events. It is also evident that beingfitted in an open environment, these parts are potentially at risk ofdamage from unknown resilient foreign bodies thrown up from the road atgreat speed.

Embodiments illustrated in FIGS. 4-9 and described hereinbelow whereverpossible have common numbering with FIGS. 1-3.

FIG. 4 illustrates a first embodiment of the present invention fitted tothe suspension assembly illustrated in FIGS. 2 and 3. The embodiment isa weighing system comprising a transducer (11) intimately mounted on oradhered to a strut (3) and a reference device (12) for monitoring theinclination of the chassis (4) or body (5) mounted remotely from thesuspension components. A supervisory device (not shown in the drawings)monitors the transducers (11, 12). From a knowledge of signal outputs atseveral fixed positions (established on fitting and subsequentinstallation checks), the supervisory device is able to infer the stateof loading or of overload of a vehicle in service. The reference device(12) moderates the behaviour of the supervisory device in order to takeaccount of vehicle use on an incline.

FIG. 5 illustrates a second embodiment of the present invention fittedto a suspension assembly comprising an airbag spring (13).

FIG. 6 illustrates a third embodiment of the present invention fitted toa leaf spring suspension assembly. The hub (7) is connected to the leafspring (17) by saddles and u-bolts (15). The leaf spring (17) is held inplace on the chassis (4) by a set of pins and shackles (16,18) whichconstrain the movement of the spring (17). The transducer (11) isintimately mounted on the leaf spring (17).

FIG. 7 illustrates a fourth embodiment of the present invention fittedto a trailing arm type or rubber suspension assembly. The latterutilises a short arm (19) to support the hub (7). The short arm (19) isconstrained to move by rubber supports which react to movement of theshort arm (19) relative to the chassis (4).

In all of these Figures, the necessary electrical cabling or anypowertrain or driveshaft components are omitted for the sake of clarity.

FIG. 8 shows a schematic layout of an embodiment of the presentinvention. A transducer (11) is mounted on a suspension component ofeach wheel. The transducers (11) are in electrical communication withthe controller via a reference device (12) and a power supply unit(101).

The transducers (11) in this embodiment incorporate an inclinometer andcapability to generate an output signal in accordance with the measuredangle. Transducers (11) of this nature are well known in the art. Anexample of such a transducer is an Analog Devices ADXL203 Dual axisaccelerometer/inclinometer.

The reference device (12) measures the attitude of the vehicle. If thevehicle is on an incline, either longitudinally or latitudinally, theoffset experienced by the suspension components can be accounted for andthe associated threshold values (described below) adjusted accordingly.The reference device (12) therefore comprises a pair of inclinometersheld in an orthogonal relationship such that the longitudinal andlatitudinal angular displacement with respect to level can beascertained. The reference device also contains circuitry such thatsignal processing can be performed on the signals relating to theattitude of the vehicle and suspension component angles in order toincorporate them into a single output signal for the controller (100) toreceive via the power output. The man skilled in the art will appreciatethat this is a matter of convenience rather than necessity and that thesignal processing can take place in the controller.

The controller (100) comprises a microprocessor and some memory, suchthat the microprocessor can be programmed with suitable algorithms forreceiving and manipulating the signal from the reference device in orderto produce the required output representative of the load condition. Thesoftware/algorithms used for this operation require standard operationsas would be familiar to the man skilled in the art. The output signalgenerated by the controller (100) can be used by a sensory device suchas a flashing strobe light or siren which are connected via theexpansion input/outputs as connected to the power supply unit (101).There is a display unit incorporated into the controller (100). Thedisplay of the display unit can be used to show the load condition to,for example, the person loading the vehicle or driver by producing asuitable message on the display screen such as showing the percentage ofthe threshold values of the load condition. The display unit can be usedas a programming interface for programming the controller (100). Thedisplay is provided with a number of touch buttons corresponding tovarious menu options presented on the display screen, whereby theoperator will be presented with a first menu upon powering up thesystem. Navigating numerous menus will allow a user to program thecontroller for various different types of transducers (11) and forvarious different vehicles within the options setup in the controllermemory.

An example of this type of display with integral controller is a Vanscomodel number VMD1216A. This is a commercially available unit whichcommunicates using the Control Area Network (CAN) protocol which is wellknown in the art for such applications. The VMD1216A comprises anInfinian C164 micro controller, 512 kb flash (re-programmable withoutdisassembly), 128 kb of RAM and 8 kb of EEPROM. It also comprises fiveinput buttons on the face of the unit for programming the controller(100).

FIG. 9 is a flowchart illustrating the operation of an embodiment of theinvention. Each of the transducers (11) which are mounted on themoveable suspension components as shown in FIGS. 4, 5, 6 and 7 comprisean inclinometer to measure the angular displacement of the suspensioncomponent. The transducer (11) produces and outputs a signalcorresponding to the measured angular deflection. This is used by acontroller (100) to generate a signal representative of the loadcondition of the vehicle as related to the angular deflection of thesuspension component. To put the angular deflection in context, a firstset threshold values for the angular deflection experienced by thesuspension component is obtained ie the angle of the suspensioncomponent is measured whilst the vehicle is empty and while it iscarrying a full load (the so-called tare angle and load anglerespectively). These measurements are carried out on flat ground and thetyres must be properly inflated. Once the tare angle and load angle havebeen measured the corresponding output signal from the or eachtransducer (11) is fed into the controller. The controller (100) definesa relationship between the tare weight of the vehicle (which has beenpreviously measured and loaded into the controller) and the tare angle.The same is done for the load weight and load angle. The value of thetare angle is set as the tare threshold or 0% point. The value of theload angle is set as an upper'threshold point or 100% point. There is afurther lower threshold which is typically set between 60% and 98% andmore typically set at 80% of the upper threshold. Using these set pointsthe controller (100) can attribute an angular displacement with apercentage loading. As the vehicle is loaded with a load, the loadcondition can be continually monitored by the controller and an outputsignal generated when the upper threshold has been reached for a givensuspension component. This embodiment can also detect whether there isany continued disturbance during the monitoring of the load condition toascertain whether loading of the vehicle has ceased. This isaccomplished by detecting any alteration in the angular displacement inthe suspension components by comparing the average values of the angulardisplacements at different time intervals. If the vehicle is still beingloaded, a signal is generated by the controller to indicate that a loadcondition cannot be properly determined.

With reference to FIGS. 10 and 10.1, the installation, calibration andoperation of the device will be described in more detail.

Installation (201-207): The first step is to ascertain whether thetransducers (11) have been electronically (rather than mechanically)installed (201). Every time a new type of transducer (11) is used itmust be registered with the controller in order for the controller to beproperly configured for the appropriate output signal from thetransducer. Installation is achieved by selecting the model number ofthe commercially available transducer (11) from a pre-programmed listheld in the controller memory. This is done by using the menu selectionprocess described above. It is also necessary to identify whichwheel/suspension assembly the transducer (11) is placed on (eg the frontoffside) and the orientation of the transducer (11). The orientationrefers to the position of the transducer (11) relative to thelongitudinal axis of the vehicle chassis. For example, in FIG. 9, thetwo rightmost transducers (11) are represented as being in-line with thelongitudinal axis of the vehicle whereas the two leftmost transducers(11) are perpendicular for the longitudinal axis of the vehicle. Oncethis has been established, it is necessary to decide whether calibrationis required (207).

Calibration (209-221): Calibration is necessary to set the upper andlower threshold values for the system. It is required after anymaintenance on the system or the vehicle such as for example thereplacement of a suspension component or transducer. The purpose ofcalibration is to measure the angular displacement of the loaded andunloaded vehicle in order to have a reference frame within which thesystem can operate. The tare, upper and lower threshold valuescorrespond to the angular displacement of the suspension component whenthe vehicle has no load, a maximum load and between 60% and 98% (moretypically 80%) of the upper threshold respectively. In (209) theunloaded axle weights are entered into the controller and the angulardisplacement of the suspension component is measured to give the vehicletare angle. This value is then stored (213) for future reference. Thevehicle is then loaded to its maximum load weight which is achieved byloading the vehicle on a weighbridge (or weigh-pads) before measuringthe angular displacement of the suspension components (217) and storingthese values in the controller. The final calibration step (221) is toset an alarm point for both of the axles and the gross vehicle weight.

Operation (223-263): In operation, the controller cycles through acontinuous loop whereby the values from the rear transducers (11) andfront transducers (11) are continually monitored and their conditionassessed. The first step is to take the values from the rear transducers(11) (223) and use the controller to calculate a percentage loading forthe rear axle when compared to the upper threshold for the rear axle(227). The next step is clearing the motion detect warning system (225).After calculating the load for the rear axle as a percentage (227), thevalue is put through the motion filter in order to ascertain whether thevehicle is still being loaded (229). The motion filter is an averagingfilter used to compare the value of the angular displacements taken attwo separate time intervals. The controller samples the angulardisplacement over a time period and stores these values in a sample setcomprising n samples (where n is an integer). By comparing thedifference in the average of two sample sets with a pre-determinedvalue, the presence of motion can be detected. The size of the samplesets and the value of the pre-determined value are dependent on thedynamic properties of the vehicle in question. The factors to beconsidered are the amount of deflection and the frequency of oscillationto be accounted for. If the percentage loading for the rear does notpass through the limits of the motion filter, a warning is displayed onthe display unit (100) and the controller returns to step (223) to readthe values from the rear transducer again. This process is repeateduntil the motion detector confirms there is no further disturbance inthe vehicle as a result of loading upon which time the controllercaptures the values from the front transducers (231) and calculates thepercentage loading for the front axle (233). The percentage value forthe front axle is fed through the motion filter and if the limits areexceeded, the display unit (100) motion detect warning system isactivated and the controller turns to step (223). This process isrepeated again until the percentage loading for the front axle passesthrough the motion filter. The controller then calculates the totalpercentage loading of the vehicle on the basis of the front and rearaxle loadings prior to passing the value through the motion filter. Ifthe value does not pass through the motion filter, the display unit(100) displays motion detect warning and the controller returns to step(223). However, if the value passes through the motion filter thecontroller compares the loading values to the alarm set points whichcorrespond to the threshold values for the upper limits as set in (221).If the rear alarm set point has been reached (241), the controllerchecks whether the display is displaying the motion detect warning. Ifit is, the controller returns to step (223). If not the display unitoverload alarm output is activated (257) and a buzzer is sounded (259).Having sounded the alarm the controller returns to step (223) via (261).The same process is repeated for the front alarm set point and the totalalarm set point (243, 245). If the alarm set points have not beenreached for either the rear, front or total percentage of vehicleloading values then the controller proceeds to step (247). A comparisonof the percentage loading to the rear lower threshold is then executed.If the controller detects that the lower threshold has been exceeded thedisplay unit is checked to ascertain as to whether the motion detectwarning displayed. If the motion detect warning system is activated thecontroller returns to step (263). If the motion detect warning is notdisplayed then the near overload warning system is activated causing anear overload siren to be sounded. If, on the other hand, the lowerthreshold is not exceeded in any of the rear then a check is made toascertain whether the display unit (100) is displaying the detectwarning yet again. If it is not then the display unit (100) signals thatthe loading is safe. If there is motion detected then the controller(100) returns to step (263). This process is repeated for the front andtotal percentage loading values.

What is claimed is:
 1. A system for indicating a weight of payload of avehicle having suspension components, the system comprising: a staticgravity-sensing accelerometer mounted on at least one suspensioncomponent of a suspension assembly, positioned between a vehicle chassisand a wheel hub, and configured as an inclinometer to measure adeflection angle of the at least one suspension component; a controllerconfigured to generate an output signal representative of the weight ofpayload of the vehicle, wherein the controller uses based upon acomparison of the measured deflection angle of the at least onesuspension component to generate the output signal a predeterminedthreshold and generate the output signal when the measured deflectionangle reaches the predetermined threshold; and a sensory output devicewhich indicates the weight of payload of the vehicle in response to theoutput signal of the controller; wherein the controller is configured tocompare the measured deflection angle of the at least one suspensioncomponent to a predetermined threshold and generate the output signalwhen the measured deflection angle reaches the predetermined threshold.2. The system as claimed in claim 1, further comprising: at least onereference device adapted to generate a reference signal relating to theattitude of the vehicle, wherein the controller is further configured toreceive the reference signal and adapt the output signal representativeof the load condition to account for a variance in the measureddeflection angle of the suspension component created by the attitude ofthe vehicle.
 3. The system as claimed in claim 1, wherein the sensoryoutput device comprises a display configured to show the load conditionof the vehicle.
 4. The system as claimed in claim 1, wherein the sensoryoutput device comprises a flashing strobe light, a siren, or a buzzer.5. The system as claimed in claim 1, wherein the at least one of aninclinometer or an accelerometer comprises a wireless signal transmitterand wherein the controller comprises an associated wireless signalreceiver such that the at least one of an inclinometer or anaccelerometer and the controller may communicate with each other over awireless channel.
 6. A method of monitoring the weight of payload of avehicle having suspension components, the method comprising: monitoringa suspension assembly by determining a deflection angle of at least onesuspension component of the suspension assembly, positioned between avehicle chassis and a wheel hub, using a static gravity-sensingaccelerometer this is configured as an inclinometer and mounted on theat least one suspension component and configured as an inclinometer;comparing the deflection angle of the at least one suspension componentto a predetermined threshold; generating an output signal which isrepresentative of the weight of payload of the vehicle when thedeflection angle reaches the predetermined threshold; and using theoutput signal to activate a sensory output device which indicates theweight of payload of the vehicle.
 7. The method as claimed in claim 6,wherein the sensory output device shows the load condition of thevehicle on a display.
 8. The method as claimed in claim 6, wherein thesensory output device displays or sounds at least one of an overloadwarning or a near overload warning.
 9. The method as claimed in claim 6,further comprising: monitoring the deflection angle of the at least onesuspension component at two separate time intervals; determining thedifference of the deflection angles from the two separate timeintervals; and generating a disturbance signal indicating that motion isdetected if the difference is greater than a predetermined amount. 10.The method as claimed in claim 6, further comprising: sampling themonitored deflection angle at discrete intervals and storing the sampleddata as n sample sets each comprising a number of samples, where n is aninteger; and generating a disturbance signal indicating that motion isdetected if the difference between two successive sample sets is greaterthan a predetermined value.
 11. A method of monitoring the weight ofpayload of a vehicle having suspension components, the methodcomprising: monitoring a suspension assembly by determining a deflectionangle of at least one suspension component of the suspension assembly,positioned between a vehicle chassis and a wheel hub, using a staticgravity-sensing accelerometer mounted on the at least one suspensioncomponent and configured as inclinometer; comparing the monitoreddeflection angle to a predetermined threshold; and activating a sensoryoutput device when the monitored deflection angle reaches thepredetermined threshold.
 12. The method as claimed in claim 11, whereinthe sensory output device indicates the load condition of the vehicle.13. The method as claimed in claim 11, wherein the sensory output deviceshows the load condition of the vehicle on a display.
 14. The method asclaimed in claim 11, wherein the sensory output device displays orsounds at least one of an overload warning or a near overload warning.15. The method of claim 11, wherein the vehicle is a commercial vehicle.16. The method of claim 11, wherein the at least one suspensioncomponent is selected from the group consisting of a strut, a leafspring, a trailing arm, and a short arm.
 17. The system of claim 1,wherein the vehicle is a commercial vehicle.
 18. The system of claim 1,wherein the at least one suspension component is selected from the groupconsisting of a strut, a leaf spring, a trailing arm, and a short arm.19. The method of claim 6, wherein the vehicle is a commercial vehicle.20. The method of claim 6, wherein the at least one suspension componentis selected from the group consisting of a strut, a leaf spring, atrailing arm, and a short arm.
 21. A system for indicating a weight ofpayload of a vehicle, the system comprising: a suspension assembly; astatic gravity-sensing accelerometer mounted on at least one suspensioncomponent of the suspension assembly, positioned between a vehiclechassis and a wheel hub, and configured as an inclinometer to measure adeflection angle of the at least one suspension component; a controllerconfigured to generate an output signal based upon a comparison of themeasured deflection angle of the at least one suspension component to apredetermined threshold and generate the output signal when the measureddeflection angle reaches the predetermined threshold; and a sensoryoutput device which indicates the weight of payload of the vehicle inresponse to the output signal of the controller.
 22. A system forindicating a weight of payload of a vehicle, the system comprising: avehicle suspension assembly; a static gravity-sensing accelerometer,mounted on the vehicle suspension assembly in a position between avehicle chassis and a vehicle wheel hub, that functions as aninclinometer to measure a deflection angle of at least one suspensioncomponent of the suspension assembly; a controller that generates anoutput signal when the measured deflection angle of the at least onesuspension component reaches a predetermined threshold; and a sensoryoutput device that indicates the weight of payload of the vehicle inresponse to the controller's output signal.